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Electrical Engineering · FE Electrical · Professional Certifications

FE Electrical: AC Circuits and Phasors

Sinusoids, phasors, impedance, resonance, RLC transients, power factor, complex power and three-phase basics.

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45 basic cards for FE Electrical Electrical Engineering. Set 1 of 6 in FE Electrical. It opens with "General form of a sinusoid in AC circuits" and "Relationship between RMS and peak voltage". More Professional Certifications decks are listed below.

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General form of a sinusoid in AC circuits
Show answerv(t) = Vm*sin(wt + phi), where Vm is peak voltage, w is angular frequency (rad/s), and phi is phase angle
Relationship between RMS and peak voltage
Show answerVrms = Vpeak / sqrt(2), approximately 0.707 times the peak value
What is phase angle in a sinusoid?
Show answerThe angular offset (in degrees or radians) that determines the sinusoid's starting point at t=0
Relationship between frequency, period, and angular frequency
Show answerT = 1/f and w = 2*pi*f, where T is period, f is frequency in Hz, and w is angular frequency in rad/s
Definition of a phasor
Show answerA complex number representation of a sinusoid, written as V = Vm @ phi or V = Vm*exp(j*phi)
Convert sinusoid v(t) = Vm*sin(wt + phi) to phasor form
Show answerExtract magnitude Vm and phase angle phi, then express as phasor V = Vm @ phi in the frequency domain
Main advantage of using phasors in circuit analysis
Show answerPhasors convert sinusoidal differential equations into algebraic equations, simplifying AC circuit analysis
Definition of impedance
Show answerZ = R + jX, the complex opposition to current flow, with resistance R (real part) and reactance X (imaginary part)
Inductive reactance formula
Show answerXL = w*L = 2*pi*f*L, in ohms, where L is inductance and w is angular frequency
Capacitive reactance formula
Show answerXC = 1/(w*C) = 1/(2*pi*f*C), in ohms, where C is capacitance and w is angular frequency
Impedance of a series RLC circuit
Show answerZ = R + j(wL - 1/(wC)) = R + j(XL - XC), where reactances can be positive or negative
Definition of admittance
Show answerY = 1/Z, the reciprocal of impedance, measured in siemens (S), inverse of resistance or impedance
Ohm's law in phasor form
Show answerV = Z*I, where V is phasor voltage, Z is impedance, and I is phasor current
Voltage divider formula for impedances
Show answerVout = Vin * (Z2 / (Z1 + Z2)), generalizing the resistive divider to complex impedances
Condition for resonance in a series RLC circuit
Show answerXL = XC, or wL = 1/(wC), making the imaginary part of impedance zero

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